The invention relates to a tool for crushing coke in drums by means of high-pressure water jets, which has
a housing with a feed system for high-pressure water and
a housing wall with outwardly directed boring and cutting nozzles, out of the openings of which high-pressure water jets exit as well as
flow channels, which connect the feed system with the boring and cutting nozzles.
In oil refineries, the last, otherwise no longer usable, fraction of the crude oil is converted to coke. The conversion takes place by introducing this fraction to drums, which fill with coke as the operating time progresses. When the maximum fill level of the drums is reached, the coke is cut out of the drums.
This process, called “decoking”, is normally performed with high-pressure water jets, which crush the coke and flush it out of the drums. The tool for generating these high-pressure water jets is inserted into the drum from above via a boring rod. The “decoking” is performed in two sections. First, an opening is bored in the drum from top to bottom by the tool, then the tool is guided back to the top end of the drum and the coke is now crushed by the high-pressure water jets, which exit from it approximately at a right angle to the longitudinal axis of the tool.
The tool, which is for example known from DE 10 2011 053 852 A1, is thus designed for two operating states: first for the boring of an opening, which is required for moving the tool and the later discharging of crushed coke, and second for cutting the coke away from the cross-section of the drum. Accordingly, boring nozzles first send high-pressure water jets mainly parallel or also at an acute angle to an axis, which is formed by the boring rod and the opening formed during boring. Cutting nozzles in contrast generate high-pressure water jets, which are directed mainly at a right angle or at a flat angle to the axis formed by the boring rod and the opening in the drum and pass through a spiral channel for loosening, crushing and flushing out the coke when the tool with the rotating boring rod is lowered into the drum.
This results in that the cutting nozzles are inactive when the boring nozzles are activated and, vice versa, the boring nozzles are inactive when the cutting nozzles are activated. In interim periods, the boring and cutting nozzles can both be inactive.
No high-pressure water passes through an inactive nozzle from inside to outside so that there is a risk that coke particles are deposited on or in the outer opening of an inactive nozzle and the opening of the nozzle is plugged completely or partially so that the nozzle, when high-pressure water is again supplied to it from inside, cannot deliver a high-pressure water jet or only a high-pressure water jet, the jet shape of which is impaired.
It is known from WO 2012/109211 to permanently flush inactive nozzles via a bypass with pressure reduction and check valve for return flow prevention and for avoiding coke deposits on the nozzle opening. However, the construction effort for such a bypass system is relatively high. And, as a result, coke particles can still be deposited at least on the outside on the opening of the nozzle with the result that the delivery of a high-pressure water jet from the nozzle is impaired when the nozzle is activated again.
Thus, the object is to design a tool of the initially named type such that the opening of the boring and cutting nozzles is permanently protected and is kept free of deposits.